Extended time tests on GRP pipe bends

Abstract

Strain measurements were taken on two glass reinforced plastic (GRP) pipe bend specimens made by hand lay-up from polyester resin and E glass in the form of chopped strand mat. Each specimen consisted of a right angled pipe bend with straight lengths at either end. One end was clamped and the free end loaded to give in-plane flexure of the bend. One specimen was subjected to constant load conditions and the other to constant free end displacement over periods up to 329 hours, during which strains were monitored. Finally both specimens were subjected to continuously increasing load up to fracture. During the constant load test there was a little redistribution of strain, but for the constant displacement test there was considerable relaxation of outside surface strains but little change in the corresponding inside surface strains. Results are compared with those for GRP strip tests under three point bending.